Proceedings Paper

We have demonstrated for the first time that in diamonds some defects correlated with the presence of intense H-related infrared absorptions, also absorb in the visible range. These diamonds exhibit two types of optical absorption spectra, resulting in a browniqh yellow or gray color. We believe that the 1405 and 3107 cm-1 H-related infrared absorptions are not simply due to C-H vibrations, but rather to stretching modes of complexes involving hydrogen and nitrogen in all cases. These types of H-rich brownish yellow and gray diamonds - or sectors of particular stones - are probably the result of cuboid growth.